Posted
by
BeauHDon Monday February 12, 2018 @08:03PM
from the post-launch dept.

An anonymous reader quotes a report from Los Angeles Times: The center core booster of SpaceX's Falcon Heavy didn't land on a floating sea platform as intended during last week's first test flight because it ran out of ignition fluid, company Chief Executive Elon Musk said Monday. Musk took to Twitter on Monday morning to give a few more updates on the Falcon Heavy's first flight. After liftoff, the rocket's two side boosters touched down simultaneously on land, eliciting cheers and applause from the crowd of SpaceX employees gathered in the company's Hawthorne headquarters, as seen on the launch livestream. Those two boosters, which were used in previous launches of SpaceX's workhorse Falcon 9 rocket, will not be reused again, Musk said in a post-launch news conference last week. But the center core booster ended up hitting the Atlantic Ocean at 300 mph and about 328 feet from the floating platform where it was supposed to land. Musk said Monday that there wasn't enough ignition fluid to light the outer two engines of the booster "after several three engine relights."

Not sure the point you are trying to make here... It was a test flight. The first time they have had to slow down a booster from this sort of burn, with the longest set of three engine burns so far.

Turns out the current build doesn't have enough igniter fluid. But they captured that data, and can now correct for it.

It is exactly the same thing that happened with the early test landings of the Falcon 9 boosters, where they weren't sure how much hydraulic fluid they would need. Now they know, and now they land the Falcon 9 boosters with an incredible success rate.

They can't just calculate exactly how much they need of these things, because the atmosphere adds a highly dynamic variable. They can take a very educated guess, but as the landing is automated and corrects for a wide variety of conditions, this is one of those "we have to do it to see... and we might not even get it right the second... or third... or fourth time."

I agree with you for the most part. My one surprise in all of this is that they don't over-design the first vehicle. I'd have expected them to give themselves 15% more than they calculated they needed, and then observe "oh hey, we only needed 2% more than we thought" when it landed.

On the other hand, I guess maybe they did do that, and discovered that they needed 17% more than they thought.

You would think with something like ignition fluid they would just go 100% more right off the bat, and see how much they actually use. It has to be a teeny tiny fraction of the total rocket's weight. Yeah, it would mean having to build larger storage tanks for it, too, but if it saves your multimillion dollar rocket from performing the worlds largest cannonball....

We don't really know how much they actually included. For all we know they already had increased the quantity to what they thought was a safe margin.

The balancing act is pretty insane, any increase in rocket mass means a decrease in payload mass. They literally have to build a rocket that's just equipped to do what it needs to do in order to maximize payload. After all, a rocket is cool and all but it's the payload that really matters.

If they do decide to add more fluid then they'll probably see if they can cut mass anywhere else. It may not take much, but finding 50-100lb is going to be a challenge.

Sure, but this is a TEST flight, so I would argue that it's more important to start with a smaller payload. That way you can work down from safe to probably safe and have less risk of losing the test vehicles.

Sure, but this is a TEST flight, so I would argue that it's more important to start with a smaller payload. That way you can work down from safe to probably safe and have less risk of losing the test vehicles.

Well, it's less risk to the test vehicle but the more your final configuration deviates from the current configuration the higher the risk of some unexpected side effects. When you can count the number of tests on one hand with fingers to spare it's better to fail on the first test and say that's what tests are for than fail on the second test and raise concerns that it has hidden flaws that might kill missions at random. Despite all that Elon Musk said to manage expectations they did not send a $100 million dollar rocket out there to blow up an equally expensive pad on a 50-50 or 2/3rds chance. They've extensively tested every component and subsystem they could find, simulated it a million times with computers and it would have passed with flying colors.

This is the final integration test, not the first test. The rest is that X factor, what haven't we taken into consideration. Are our assumptions, models and formulas flawed in some way. He can't really lose talking it down, if it blows up on the pad well space is hard. If it works, he's pulled off some amazing feat. So I'd want something very close to the production model flying, as long as the odds remain good you'll get your test data. And in that respect this was an entirely insignificant failure, they got telemetry on everything right up to the final impact. Making this part of the mission fail-safe wouldn't really have any big benefit. Just downsides in redesign, if this was what they thought was the right amount.

For a test launch with a minimal payload they had plenty of capacity to spare. That rocket was capable of launching 37,000 pounds out past Mars. Granted that's in the fully expendable mode; I'm not sure what the capacity is when recovering all 3 stages but extrapolating from the figures they provided for LEO and GTO it should still easily exceed 4,000 lbs when launching towards Mars. Meanwhile the roadster clocks in at 2,800 with the batteries in; much less after they removed those.

It's a minuscule amount of the booster's mass, and mass is less important on the first stage anyway, but it's also a volatile fluid that spontaneously ignites on contact with air. You have more reasons than mass to want to minimize the quantities you're working with, especially when working with experimental hardware where things may go wrong.

You would think with something like ignition fluid they would just go 100% more right off the bat, and see how much they actually use.

There's also the issue that the ignition compounds are 1) toxic and pyrophoric crap and 2) gunk up the engines, so you don't really want to carry more than what you need because either people in hazmat equipment would need to deal with safely removing it after landing, or alternatively, you'd have to use it all up during the last ignition and then deal with the gunk.

One thing that I don't see mentioned is that it would appear this was the first time they attempted to actually land using a multi-engine descent. All of the prior landings (not counting the one deliberately ditched at sea) used a single engine to stick the landing. They are eager to get multi-engine descent working because it will allow them to land boosters with less fuel.

Correct - I don't think that counted as a "landing", or even an attempting landing... the intent was always to have it descend into the ocean. It sounds like this mission was their first attempt to actually land using the three-engine burn.

Because this was a test flight, and they needed to verify that separating and landing the side boosters worked. Now they need to verify that in doing all of that, no damage got caused to them, so very likely they're going to completely take them apart and look at every component in detail.

That's a very insightful question. I guess they did it to keep practising the landing, or to do the first double landing and get the nice video that they got, or maybe so that they can disassemble the rockets and reuse or recycle some materials.

To save people video watching:In the post-flight press conference, Musk said that the titanium grid fins are hard to manufacture and expensive and they currently don't have many, so he was very pleased to get these ones back. Also, the titanium grid fins are larger, and the side boosters need the bigger fins because the nose cone (rather than blunt end) reduces the effectiveness of the fins.

The problem though isn't just touching at ~1m/s, it's touching within 89 meters of the landing pad radius. Parachute leaves the rocket at mercy of random winds. Soyuz is considered landing "on the spot" when it lands within 1.5km of the planned point.

Even in science and technology, to maximize funding, sales, and valuation, you have to be shameless promoters. With the car-in-space, cheering crowds, and super-enthusiastic hosts, SpaceX's video stream of this launch had more than a touch of P. T. Barnum. I felt for the older engineering director, behind whose smiling "total success" pronouncement was probably a guy thinking "what the hell happened to my core?"

Those two boosters, which were used in previous launches of SpaceX's workhorse Falcon 9 rocket, will not be reused again, Musk said in a post-launch news conference last week.

Then why spend fuel and other resources on landing them?

The plan is to only use only Block 5 modules from here onwards but this maiden launch gave them a chance to test recovery using expendable boosters.Even if reuse is not being considered, I'm sure there's plenty to recycle.

Those two boosters, which were used in previous launches of SpaceX's workhorse Falcon 9 rocket, will not be reused again, Musk said in a post-launch news conference last week.

Then why spend fuel and other resources on landing them?

It's possible some of the parts can be refurbished and reused, even if the entire booster won't be. Also, having them all in one piece allows everything to be studied for wear and possible failure points and help refine future boosters.

As a highly rated reply said, "practice". I'd like to add that it's also the only nominal way to land them. The alternative is to make a mess on the LZ, or chuck them someplace where they'd be pollution.

As a highly rated reply said, "practice". I'd like to add that it's also the only nominal way to land them. The alternative is to make a mess on the LZ, or chuck them someplace where they'd be pollution.

Of course; but this one's not designed to do that. If you're committed to the Falcon style of recovery, the parachute system is dead mass. In space flight, mass is money so you sort of have to commit to one recovery system or another.

Musk is on record as saying that out of everything that could have been recovered, those two side boosters are the things he most wanted back. They have the upgraded titanium grid fins on them which can and will be re-used, and are seemingly a) very hard to make and b) expensive as hell.

As a side note, putting a nose cone on an F9 core drops the grid fins performance by 30%, so those grid fins may actually be the only 2 in existence since they had to make them larger to account for that

I believe I saw one quote from Elon somewhere that even thought they won't be re-used in entirety there will be some re-use of expensive (in time and money) parts from them. In particular I think he mentioned re-use of the grid fins.

According to the post-launch press conference, they landed them because they wanted the grid fins back. Apparently they're rather expensive machined titanium, and were specially made for the "heavy" configuration.

Elon Musk said that the two side boosters were using the newly developed titanium guidance fins - and he's happy those two landed fine as those things were expensive and will be reused for other Falcon9 boosters. The center one used the old-style fins (you can see in the pre-launch photos, the fins look different).

Given this was a first launch of something so complex it is amazing more didn't go wrong. Sure simulators have vastly reduced the risk (probably not a Kerbal Space Enterprise Edition;) ), but simulators are still not a good replacement for real world testing.

If it was only a lack of ignition fluid, then that seems like an easy fix, compared to all the other variables they have to deal with.

The ignition fluid in question is TEA-TEB https://en.wikipedia.org/wiki/Triethylborane#Rocket [wikipedia.org], a mixture of triethylborane and triethylaluminium. This is a common ignition fluid for rockets which burn RP-1 (rocket grade kerosene), since RP-1 is hard to ignite. The two are mixed because one of the two has really dependable ignition while the other one burns more cleanly. This sort of ignition system has been in use since the 1960s, but SpaceX is the first to use the TEA-TEB ignition system to ignite a rocket engine while the rocket engine is moving quickly *downwards* into the atmosphere. Experiments will sometimes work, and sometimes won't. They are obviously figuring out just how much TEA-TEB they need.

Experiments will sometimes work, and sometimes won't. They are obviously figuring out just how much TEA-TEB they need.

That's what seems odd. They've re-lit Falcon engines dozens of times by now. I'm surprised the amount of igniter varies by much so I expected the knew how much they needed. Does the amount of igniter vary much based on, say, the speed and altitude of the booster? Do those parameters vary by that much between normal Falcon 9 and the Falcon Heavy flights?

I'm guessing it must vary by more than I expect. These guys are rocket scientists after all. If it was that simple and predictable, we wouldn't have a new cl

It's unclear to me if the 1kg and 25000kg ball have the same terminal velocity, but the side cores and center core aren't the same shape. The center core is taller...

Assuming both objects are falling on their face and not flipping (the way that the Falcon 9 travels), a penny will fall slower in atmosphere than a long cylinder with the same density and area, even if the orientation of travel of both is in the direction of the surface of the penny. This is because the air resistance of the penny per uni

Apparently during ignition TEA-TEB is kept running until engine parameters are within the "I am working correctly" range. Consumption changes depending on various conditions such as engine temperature or air speed, which were different for the center core.SpaceX has a lot of experience restarting those engines in Falcon 9 conditions, but this is still rocket science - theory is not always good enough.

Remember how a Falcon rocket ran out of hydraulic fluid for steering during sea landing? They had not enough

Apparently during ignition TEA-TEB is kept running until engine parameters are within the "I am working correctly" range. Consumption changes depending on various conditions such as engine temperature or air speed, which were different for the center core.

Ah. I see. That makes a ton of sense. Thanks. This is truly news for nerds, stuff that is totally irrelevant to our daily lives.

Of the possible failures that could have occurred, this seems like the best one. This was the newest part on the whole 'kit' so it wouldn't surprise me if it was an issue in calculations or some minor mechanical issue that resulted in this. In the end this was still an 80% success and were this a commercial launch, the buyer wouldn't have been overly disappointed since the payload made it into orbit. I have no doubt the next launch will be a complete success with all 3 rockets landing without problem. A big

The target orbit was one that went at least to Mars orbit. There were no requirements that it only go to Mars orbit. They burned to depletion to demonstrate the amount of second stage performance available after a 6 hour coast (that being a requirement of some defense launches).

Musk wanted the farthest he could get, to show capability. If he could get out of the solar system he would have. Not to mention Mars is not really a commercial destination, but there has been a lot of interest recently in asteroids as a source of minerals. He's just shown the world he can get there with car-sized equipment for $90m.

Of the possible failures that could have occurred, this seems like the best one. This was the newest part on the whole 'kit' so it wouldn't surprise me if it was an issue in calculations or some minor mechanical issue that resulted in this. In the end this was still an 80% success and were this a commercial launch, the buyer wouldn't have been overly disappointed since the payload made it into orbit. I have no doubt the next launch will be a complete success with all 3 rockets landing without problem

Don't skimp on the metrics! The mission was 100% success given it launched successfully and put the payload into high orbit. All buyers would be perfectly satisfied with the result. The landings of 2/3 boosters is extra, and the reignition of the second stage to achieve Mars trajectory was extra - although the angle was slightly off. I'd grant these an additional 50% bonus so 150% successful mission far beyond anyone's expectations. Even Musk said he'd be happy if it blew up far enough from the launch pad to not cause damage.

Finding out potential problems in a design can be daunting task, especially when something going wrong causes it to explode. What this means is they have found how to improve the design and will likely factor this into other designs. It's only a true failure if you don't learn anything in the process.

~$5 million for the centre core IIRC, and it wasn't going to be reused in any case. All-in-all, fairly cheap in aerospace terms for valuable data.

Sometimes there's no substitute for actually trying things out and failing. Aiming to succeed but not being afraid to fail is one of the major reasons why SpaceX has advanced their development so quickly (even with a 5-year delay on original estimates for the first Falcon Heavy test flight).

Was hard not to. Felt like one of those "Holy shit, humanity... Holy shit." moments.
Shit coming back from space and landing without banging off the ground or splashing into the water... is pretty amazing. Even cooler that the entire thing is autonomous.

Not enough ignition fluid to light the outer two engines after several three engine relights. Fix is pretty obvious.

Somebody then turned those 19 words into an article, which/. then summarized to about 200 words. Furthermore, Musk's tweet didn't tell us anything he hadn't already said in the post-launch press conference.

There actually was some news in Musk's recent twittering, however: An extra drone ship is being constructed for the east coast, to be named A Shortfall of Gravitas.

I don't know why the LA Times is reporting this as new news. I'm pretty sure I had heard by Wednesday or Thursday that the problem was the rocket rant out of TEA-TEB ignition fluid. Don't journalists watch press conferences and read analysis anymore? Does the CEO need to Tweet about it before they pay attention?

I pointed this out in great detail on the discussions of the governor of Hawaii being unable to alert people that the missile strike was false due to not knowing his twitter login, but yes. Yes this is the world we live in. Journalists have been cut left and right. There's no longer armies of people to send to press conferences. Instead people automatically monitor twitter of key public figures of interest and then post something about the tweet.

Whenever I see 328 feet, I know that someone said "about 100 meters" and the reporter multiplied it under the assumption that us yokels can't figure out what it means without their help. It really pisses me off when reading an article about something slashdot-worthy, like a rocket. We never went metric in the US, but you'd have a hard time finding one of us today who isn't bilingual enough to grasp 100 meters as easily as 100 yards or 300 feet.

On the other hand, if the SpaceX guy did the conversion because he knew that the moronic reporters would otherwise report it as "328 feet, 1.00788 inches", I withdraw my objection with a chuckle.

Much earlier than that, in the mid-to-early 1800s, the US allowed metric units to be used, and the US customary units were defined in terms of metric units, which was codified in the Mendenhall Order of 1893. So, in that sense, you could say that the US has been on a metric standard for over 100 years.

I think the biggest difference between the government space programs and the private space programs is the private programs will be advertising supported. Much of the SpaceX Falcon Heavy launch was just designed to be good TV; next time expect the rockets to be emblazoned with Durex ads!

You're not entirely right - perhaps the very first launch vehicle adorned with an advertisement was the booster that lifted the Zvezda module to the ISS. And that was a government flight, it's just that the government desperately needed more money.

for those of you wondering: just how hard is it to light a rocket engine, when it is spewing tons of highly combustible fuel and oxider per second, Scott Manley provides a handy video on rocket ignition technology [youtube.com].

For anyone that missed the interview on 60 Minutes a while back before the FH launch, it's extremely interesting to see Musk's reaction when the subject of resistance from Neil Armstrong and the late Gene Cernan's testimony to Congress. He got very emotional when pressed about the disparaging comments about the program were made and you could tell that it really hurt him personally when his heroes dissed him.
It's one of the few times I have ever seen Elon Musk let something 'get to him' and it shows a

OMG! WTF!
I meant to say that "As far as I can tell, Armstrong wasn't commenting about THIS launch." Meaning they were more about BFR...My brain obviously disengaged.
Holy crap I wish I could/. had an edit feature. Thanks for catching that and giving me a chance to clarify before more people saw it and thought I was dissing Neil (as much as I disagreed with some of his testimony).

It is amazing what Musk has done. Still, Rocket technology, isnt exactly the most sustainable thing, when you consider the amount of resources which are used. Its also, kind of low tech, we are talking explosions and so on here. What would really be an advance is an anti-gravity electromagnetic drive of some kind powered by clean energy extracted from the aether without the use of dirty nuclear and fossil fuels. Pull that off and then I will be REALLY impressed.

SpaceX's eventual plans to go to Mars utilize a different rocket engine - the Raptor [wikipedia.org]. Among other differences from the Merlin enigne (used by the Falcon 9), the Raptor will have spark ignition: no need for these highly combustible lighter fluids.